1. Field of the Invention
The present invention relates to an induction hardening apparatus, an induction hardening method, an induction heating coil, a heat treatment apparatus, and a heat treatment method, and more particularly to a technology for improving heat treatment efficiency and performing a uniform treatment.
2. Description of the Related Art
In an induction hardening method for performing a heat treatment such as high-frequency hardening with respect to a metal member, there has been known a heat treatment apparatus adopting a single shot heating process for using an induction heating coil facing an entire treatment target region to collectively perform a treatment (e.g., Jpn. Pat. Appln. KOKAI Publication No. 2005-120415, Jpn. Pat. Appln. KOKAI Publication No. 2002-174251, or Jpn. Pat. Appln. KOKAI Publication. No. 2004-44802). In such a heat treatment apparatus adopting the single shot heating process, the induction heating coil is formed into a shape associated with the entire treatment target region. For example, an annular induction heating coil is arranged to face a treatment target portion when the treatment target portion has a circular shape, and a tabular induction heating coil is arranged to face a treatment target portion when the treatment target portion has a planar shape. Since such a heating apparatus adopting the single shot heating process uses the induction heating coil to cope with various shapes and sizes of a treatment object and a treatment target portion, a large induction heating coil is required and high-output power is needed when the treatment object and the treatment target portion are large.
On the other hand, there has been known a scanning heat treatment apparatus for sequentially performing a heat treatment and a cooling treatment while relatively moving an induction heating coil, which faces a part of a treatment target portion alone, with respect to the treatment target portion (e.g., Jpn. Pat. Appln. KOKAI Publication No. 2005-89803, or Jpn. Pat. Appln. KOKAI Publication No. Sho 60-116724). In such a scanning heat treatment apparatus, the induction heating coil is formed into a shape associated with a part of the treatment target portion.
The technology of the induction heating has the following problems. That is, in the induction hardening apparatus adopting the single shot heating process, since the induction heating coil associated with a size or a shape of the treatment target portion must be used, for example, when the treatment target portion has a complicated shape, a shape or condition setting of the induction heating coil becomes complicated, and realizing the apparatus is impossible. Furthermore, when the treatment target portion is large, and a big induction heating coil is required, this results in a problem that high-output power is required. Moreover, when the treatment object is deformed due to, e.g., thermal expansion at the time of induction heating, maintaining an appropriate dimension between the induction heating coil and the treatment object is difficult. Therefore, the induction heating coil must be set to have a larger size in advance, and hence a problem of poor heating efficiency occurs.
On the other hand, in the scanning heat treatment method, when the induction heating coil is formed into a shape associated with a part of the treatment target portion, a treatment area per unit time is small, a treatment time is increased, and treatment efficiency is deteriorated. Additionally, in the case of moving the induction heating coil while continuously performing the heat treatment and the cooling treatment, for example, when an annular treatment target portion is to be treated, there occurs a problem of generation of a soft zone, which means the necessary hardness cannot be obtained at a boundary between a start portion and an end portion of the treatment.
Therefore, it is an object of the present invention to provide a technology that can readily realize a heat treatment for a desired region to be heated without requiring high power, a technology that enables a uniform treatment, and a technology that enables improving heat treatment efficiency when performing induction heating on even a large treatment object.